/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.client;

import java.io.IOException;
import java.lang.InterruptedException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.client.Row;

/**
 * Utility class for HTable.
 * 
 * 
 */
public class HTableUtil {

  private static final int INITIAL_LIST_SIZE = 250;

  /**
   * Processes a List of Puts and writes them to an HTable instance in
   * RegionServer buckets via the htable.put method. This will utilize the
   * writeBuffer, thus the writeBuffer flush frequency may be tuned accordingly
   * via htable.setWriteBufferSize. <br>
   * <br>
   * The benefit of submitting Puts in this manner is to minimize the number of
   * RegionServer RPCs in each flush. <br>
   * <br>
   * Assumption #1: Regions have been pre-created for the table. If they
   * haven't, then all of the Puts will go to the same region, defeating the
   * purpose of this utility method. See the Apache HBase book for an
   * explanation of how to do this. <br>
   * Assumption #2: Row-keys are not monotonically increasing. See the Apache
   * HBase book for an explanation of this problem. <br>
   * Assumption #3: That the input list of Puts is big enough to be useful (in
   * the thousands or more). The intent of this method is to process larger
   * chunks of data. <br>
   * Assumption #4: htable.setAutoFlush(false) has been set. This is a
   * requirement to use the writeBuffer. <br>
   * <br>
   * 
   * @param htable
   *          HTable instance for target HBase table
   * @param puts
   *          List of Put instances
   * @throws IOException
   *           if a remote or network exception occurs
   * 
   */
  public static void bucketRsPut(HTable htable, List<Put> puts)
      throws IOException {

    Map<String, List<Put>> putMap = createRsPutMap(htable, puts);
    for (List<Put> rsPuts : putMap.values()) {
      htable.put(rsPuts);
    }
    htable.flushCommits();
  }

  /**
   * Processes a List of Rows (Put, Delete) and writes them to an HTable
   * instance in RegionServer buckets via the htable.batch method. <br>
   * <br>
   * The benefit of submitting Puts in this manner is to minimize the number of
   * RegionServer RPCs, thus this will produce one RPC of Puts per RegionServer. <br>
   * <br>
   * Assumption #1: Regions have been pre-created for the table. If they
   * haven't, then all of the Puts will go to the same region, defeating the
   * purpose of this utility method. See the Apache HBase book for an
   * explanation of how to do this. <br>
   * Assumption #2: Row-keys are not monotonically increasing. See the Apache
   * HBase book for an explanation of this problem. <br>
   * Assumption #3: That the input list of Rows is big enough to be useful (in
   * the thousands or more). The intent of this method is to process larger
   * chunks of data. <br>
   * <br>
   * This method accepts a list of Row objects because the underlying .batch
   * method accepts a list of Row objects. <br>
   * <br>
   * 
   * @param htable
   *          HTable instance for target HBase table
   * @param rows
   *          List of Row instances
   * @throws IOException
   *           if a remote or network exception occurs
   */
  public static void bucketRsBatch(HTable htable, List<Row> rows)
      throws IOException {

    try {
      Map<String, List<Row>> rowMap = createRsRowMap(htable, rows);
      for (List<Row> rsRows : rowMap.values()) {
        htable.batch(rsRows);
      }
    } catch (InterruptedException e) {
      throw new IOException(e);
    }

  }

  private static Map<String, List<Put>> createRsPutMap(HTable htable,
      List<Put> puts) throws IOException {

    Map<String, List<Put>> putMap = new HashMap<String, List<Put>>();
    for (Put put : puts) {
      HRegionLocation rl = htable.getRegionLocation(put.getRow());
      String hostname = rl.getServerAddress().getHostname();
      List<Put> recs = putMap.get(hostname);
      if (recs == null) {
        recs = new ArrayList<Put>(INITIAL_LIST_SIZE);
        putMap.put(hostname, recs);
      }
      recs.add(put);
    }
    return putMap;
  }

  private static Map<String, List<Row>> createRsRowMap(HTable htable,
      List<Row> rows) throws IOException {

    Map<String, List<Row>> rowMap = new HashMap<String, List<Row>>();
    for (Row row : rows) {
      HRegionLocation rl = htable.getRegionLocation(row.getRow());
      String hostname = rl.getServerAddress().getHostname();
      List<Row> recs = rowMap.get(hostname);
      if (recs == null) {
        recs = new ArrayList<Row>(INITIAL_LIST_SIZE);
        rowMap.put(hostname, recs);
      }
      recs.add(row);
    }
    return rowMap;
  }

}
